British citizens who are poor or unemployed could be prevented from marrying the spouse of their choice if new family migration proposals become law.

The government wants to introduce a new minimum income threshold for those looking to sponsor a spouse, partner or dependants to come to the UK.

Under the proposals the unemployed or those living on less than around £5,000 a year would be banned from doing so, while the probation period before spouses and partners can apply for settlement in Britain would be raised from two to five years.

A Home Office consultation paper published on Wednesday also proposes making it more difficult for families to bring dependant grandparents to live with them in the UK. Instead, it encourages people to send money to support them abroad.

The shakeup of the family migration route to Britain, under which 48,900 visas were granted last year, is the fourth phase of the government's plan to curb immigration abuse and reduce net migration to below 100,000 a year.

However, the Oxford University-based Migration Observatory estimates the plans contained in the paper would reduce annual net migration by no more than 8,000 a year.

Restrictions on the number of non-European skilled workers and overseas students have already been announced, and there will a reduction in the rights of temporary workers who wish to settle in the UK.

The immigration minister, Damian Green, said the proposals would encourage "better family migration" and were designed to end abuses and send a message that "if you can't support your foreign spouse or partner, you cannot expect the taxpayer to do it for you".

The majority of those who come to Britain under the family route are women from Pakistan, India and Bangladesh. The consultation proposes tougher English language standards and a more "rigorous" approach to sham marriages including a new test to establish whether relationships are genuine by investigating whether the couple live together, speak the same language and knew each other before getting married.

Ministers also want to change the wording of article 8 of the European convention on human rights – which protects the right to family life – to allow even genuine wives and husbands to be deported if they have been living in the UK illegally.